I just finish the donut course of blender guru where do I go next?
I think the best way to improve on your skills is to join a community, and blender has a large community.
You could join these communities to see other people's workflow, styles and ways of working with blender.
My two favourite communities are:

Blenderartists: in this community you get to see fellow blender artist workflows, reels and the community creates challenges weekly to help you grow and learn faster. Here is the link
www.blenderartists.org

BlenderNation: is a very great community here you could get links to any tutorial in blender, assets (paid or free), documentation and so on, basically it an informative and educative community. Here is the link

www.blendernation.com